1. Field of the Invention
This invention generally relates to an arrangement for, and a method of, supplying hydrogen gas and, more particularly, to a storage tank for supplying stored pressurized hydrogen gas as a fuel to power transport vehicles.
2. Description of Related Art
Hydrogen is an excellent fuel for powering transport vehicles, particularly when environmental concerns are paramount. Hydrogen can be cryogenically stored in tanks for air transport, but not, as a practical matter, at a reasonable cost for land transport. In addition, trained crews for safely handling the hydrogen fuel are not available for land transport, as opposed to air transport.
It has been proposed to store hydrogen in tanks having hydrogen-adsorbent host materials on-board commercial land vehicles such as buses, because such storage is safe in case of tank rupture. However, experience has shown that the hydrogen interacts with the host materials over prolonged use, causing dust to be produced, thus dictating that the host materials each be relatively large-sized metal spheres on the order of about 3/4" in diameter so that the dust settles in the voids between the large aggregates, thus not clogging the gas passages and covering the surfaces of the host materials. Such large-sized metal spheres present a correspondingly small total surface area on which the hydrogen gas can be collected. This limits the amount of hydrogen that can be stored in relationship to the volume of the aggregate and its weight (if the aggregate were of smaller size, the collective surface areas would be far greater in terms of same weight and volume). Attempts to substantially reduce the size of such large-sized spheres to a powder form for increasing the total surface area presented to the hydrogen have not proven altogether satisfactory, as only the surface area of the pile of powder is exposed to the atmosphere of the storage tank, and since the powder tended to cause the tank to become clogged, particularly over repeated re-fillings of the tank. Also, the large-sized spheres had to be accommodated in a correspondingly large-sized heavy tank. However, a tank of large size and weight is not entirely suitable for cars and, in any event, detracts from energy efficiency and the benefits of compact storage as promised by the inherently small-sized, compact hydrogen molecule, absorbing on the surface of the host material. The capacity of hydrogen storage with 3/4" diameter aggregates has been seen to be twice that of the same volume tank filled solely with liquid hydrogen.